That’s how this particular moment can be summarized. All the Princesses had to do was imprison these three baddies in Tartarus. At least that way, they'd have one last chance to think on their actions and maybe seek to reform themselves and one of the show's key philosophical points that redemption is possible wouldn't have been contradicted, especially in the case of Cozy Glow, who's still only a little kid and was never even given a real backstory to explain her motivation as an antagonist. Instead, the Princesses petrified them at the urging of Discord, whose personal rule of not turning anyone to stone, along with many other things in relation to the rest of the series, was conveniently thrown out the window for this finale, ensuring they never get redeemed. Discord, meanwhile, caused this whole conflict in the first place by enabling these villains to cause as much trouble as they did, yet he is easily forgiven for his crimes and back on good terms with the friends whose trust he betrayed once again and safety he gambled with. With all this in mind, I have to wonder just what the fuck was going on in the minds of the people responsible for this bullshit. This is one part of this train-wreck of a final season that Hasbro has to officially revise so that FiM ends in a way that is well-though-out and not an insult to the franchise or its fans.